Code division multiple access (CDMA) system for calculating coefficients of filter and method for filtering a received signal

A method implemented in a Code Division Multiple Access (CDMA) system for forming a filter with filtering coefficients, wherein the filter is adapted to an equalizer of a receiver to eliminate interferences to a received signal from the receiver caused by transmission channel, the method comprising:

• a. estimating a channel response of the transmission channel;
• b. estimating a signal-to-interference-plus-noise power ratio (SINR) for the received signal from the receiver;
• c. calculating an autocorrelation function of the channel response;
• d. summing up the autocorrelation function of the channel response, a reciprocal of the SINR, and a compensation function, so as to obtain a specific function;
• e. retrieving a plurality of coefficients from the specific function;
• f. performing a cepstrum computation on the plurality of coefficients, so as to correspondingly obtain a plurality of quefrency coefficients;
• g. selecting a part of the plurality of quefrency coefficients to perform a Fourier transform with a limited size, so as to obtain a plurality of spectral components;
• h. applying an exponential computation on the spectral components, so as to obtain a plurality of exponential spectral components;
• i. applying an inverse Fourier transform with the limited size on the exponential spectral components, so as to obtain a plurality of coefficient candidates;
• j. selecting a part of the plurality of coefficient candidates, and normalizing the plurality of coefficient candidates to serve as coefficients of a denominator function of the filter, so as to form the denominator function;
• and
• k. calculating coefficients of a numerator function of the filter according to the coefficients of the denominator function and the channel response.